What is burned to keep switches from freezing ?

I've seen a few photos where switches are set a fire to keep from freezing up or getting clogged with snow. I have a picture in my head of a length of thick maritime rope (line), soaked in kerosene, then placed next to the rail, and lit. What do they really use ?

Switch heaters are usualy electric or propane.
Only time kerosene rope is used is to stretch rail after a pull apart of railjoints.

Well Meg, quite an answer! Spoken like a true "track dog". I often have passengers on my trains ask why the tracks are on fire!

I remember a few years ago that WNBC news had their helicopter broadcast a report about a fire on the railroad tracks at Jamaica Station in New York. The funny thing is it was only the switch heaters burning. They made it seem like it would cause massive delays for commuters.

...know of today's propane and electric switch heaters, before them were "smudge pots" similar to heaters once used in fileds in southern states when there was a freeze. These "pots" looked like a car muffler but had an open stack and a handle, were about 24 inches long, 8 to 10 inches wide, and maybe 4 inches high and were filled I think with kerosene or fuel oil of some kind. Anyway, maintainers and switchmen would light them and insert them between the ties at switches, sometimes two to five per switch.

The major difference being the smudge pots were adjusted to burn inefficiently to create a protective layer of smoke (hence "smudge") to reduce thermal radiation into clear air, but the RR version was designed to burn efficiently with minimal smoke to create heat.

I well recall from high school days, the large interlocking around MP7 on the CNJ 4 track mainline in Bayonne, NJ when the kerosene switch heaters were in use. Daytime they were not particularly noticeable, but at night presented a most attractive view.

I rode Amtrak Boston-Salt Lake City between a couple major snowstorms in early January 1998. The yard at Chicago Union Station had kerosene switch heaters out by the dozen. I was a little surprised that such a major yard didn't have automatic heaters. Would the automatic heaters have broken down, or would whoever owns that yard (Amtrak or Metra) have kept using kerosene ones because a big yard like that always has someone at work in it?

IF YOU GOT 'EM, LIGHT 'EM!

I say douse the things with diesel and watch the burn!

Oh, and remember the marshmallows!!!!